Even this is plenty of space to remove & install the pump, so don't cut a massive hole. Smaller is better for floor strength. And you CAN cut a short hole to be covered by a long plate, OR cut an UNDER-size hole, and then gradually enlarge it...
Before attempting to disconnect the fuel lines, read this caption:
Older fuel lines are much easier to remove.
Once they're off, and the plate is clean, use a non-sparking (brass) drift & hammer to turn the lock ring CCW. If it's stuck, the only acceptable lubricant is CLEAN MOTOR OIL. No penetrating oil; no silicone lube; no grease; no WD40.
